Carsten Bormann a écrit :
On Nov 17, 2009, at 16:08, Alexandru Petrescu wrote:
Is it efficient for the Edge Router to send a myriad of Neighbor
Advertisement messages (which are addressed to a link-layer
multicast address, and a L3 multicast address) on the backbone?
Well, we try to be fully 4861-compliant on the backbone.
Sure, that's good.
The backbone is supposed to be an Ethernet or a similar high-capacity
link, so it should have little problem with that load.
Hmm... every link has its limit. Are you sure an Ethernet would support
periodic NAs about the potentially very large number of nodes in the
6LoWPAN network?
Do we have numbers to compare?
Why cluttering the backbone?
Because that's what 4861 does to you? :-)
:-) well not quite. 4861 does require all nodes physically connected to
a link to do this periodic NS/NA but here you require the ER to do the
periodic NS/NA on behalf of potentially very large number of nodes which
are behind it.
Ethernet uses different cables from each machine, through a hub/switch,
etc. which does scales. But here we talk ER doing this stuff on a
single cable (is it 802.1q btw? how many VLANs on it?) Are we sure it
scales?
Of course, the ERs could speak a different protocol between
themselves,
Well no need of new protocol, just put the appropriate routes on them.
but the idea was to enable other nodes to live on the backbone link
and communicate with the 6lowpan nodes without requiring any
6lowpan-specific code. Those other nodes will speak 4861 only.
YEs, that's good for backbone nodes to talk to 6LoWPAN nodes through ER,
but there are much simpler ways of achieving that, other than proxy-ND:
it's either to put a route on these towards the prefix valid on the
lowpan network, or to put a default route towards the border router (not
ER) which will subsequently ICMP Redirect to it.
Now I know that's a long phrase, but it's simple in practice. I can
picture it if you wish.
Alex
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